Removes the floor restrictions for the Reverberation Ensemble receptions and also adds in ways to directly summon each member using invitations.
The UI is a bit tricky to use during the actual ensemble event, since the screen still zooms in on each layer during their phases, so while it is possible to use Keter for every single fight, actually doing so is something of a hassle since you have to edit key pages and decks on other floors and then equip them on the pre-battle screen.
However, there are also invitations that directly summon specific Ensemble members. (However, during the Ensemble event, Argalia specifically requires the Patron Librarian to be sent against him. This seems to be something set by the game itself and I don't know how to change that. The invitation version lets you use any character though.)

The invitations for summoning them are as follows:
Philip: Book of the Distortion, Unstable Book of the Crying Children
Eileen: Book of the Distortion, Book of a Church of Gears Worshipper
Greta: Book of the Distortion, Book of Pierre
Bremen: Book of the Distortion, Book of Meow
Oswald: Book of the Distortion, Book of Emma
Tanya: Book of the Distortion, Book of Gyeong-mi
Jae-heon: Book of the Distortion, Book of a Weighty Puppet
Elena: Book of the Distortion, Book of Tomerry
Pluto: Book of the Distortion, Book of Nemo
Argalia: Book of the Distortion, Book of the Purple Tear

I highly recommend the use of the No Grinding mod, not only because it makes these specific invitations a lot easier to manage (since you effectively have infinite copies of every book in the game, including the Book of the Distortion, which you can normally only get one copy of), but also because in my opinion it vastly improves the game's overall experience.